Blasting cartridge



March 24, 1942. J. BARAB BLASTING CARTRIDGE Filed Aug. 17, 1938 FIG."4

JACOB BARAB INVENTOR ATTORN FY Patented Mar. 24, 1942 BLASTING CARTRIDGE Jacob Barab, Wilmington, Del., assignor to Hercules Powder Company, Wilmington, Deb, a

corporation of Delaware Application August 17, 1938, Serial No. 225,342

6 Claims.

This invention relates to an improved blastin cartridge and to methods of production thereof. It relates more particularly to a blasting cartridge embodying a cushioning sheath which is especially advantageous in the mining of coal.

It is the principal object of this invention to provide a blasting cartridge enclosed in a sheath comprising a compressible cushioning material and a flame quenching or cooling salt. The cushioning material acts to absorb the initial shattering shock produced by firing the explosive. The cooling salt exerts a cooling or quenching effect on the gases and flame produced, thereby reducing hazards in the mine.

The sheathing of a blasting cartridge with a compressible cushioning material in accordance with this invention is of particular importance for explosive cartridges to be used in coal mining. After,the initial shock from the explosive has been absorbed by the cushioning material, the expanding gases released by the explosion search out the cleavage planes of the coal. The result is a pushing action which breaks up the structure in such a manner that large, flrm lumps are formed. Without the cushioning material, a much larger amount of pulverized coal is produced.

The improvement in blasting cartridge described in accordance with this invention may be accomplished with any desired form of explosive, but will be found most advantageous in connection with, for example, permissible dynamites of various types. The shattering effect of such explosives when fired in direct contact with coal is very undesirable. Use of permissible explosives in the process further reduces the liability of ignition of combustible gas mixtures and coal dust.

- The improved explosive cartridge which provides the advantages related above in the mining of coal may be produced in accordance with the present invention by surrounding the cartridge with a sheath comprising a non-combustible compressible material, such as, for example, expanded mica pellets or a combustible compressible material such as, for example, balsa, bagasse, cork, etc., and a flame quenching salt such as, for example, sodium bicarbonate, plaster of Paris, borax, calcium fluoride, etc. The sheath comprising the above ingredients may desirably be preformed to fit around the cartridge. The sheath may take the form of castings of semicircular sections which may be fitted around the cartridge. It may be a tube prepared by extrusion of a composition comprising the above ingredients. It may take the form of a blanket of the compressible cushioning material containing a layer of cooling salt between two layers of the cushioning material. The sheath may likewise consist of a tube of corrugated shape comprising the above ingredients, the advantage of corrugations being the added air cushioning effect provided by the air pocketed therein. Also, the sheath may consist of an annular space provided around the explosive cartridge by means of, for example, an outside paper. The compressible cushioning substance and the cooling salt may .then be loaded in the form of pellets, powder or granules into the annular space between the cartridge and the surrounding outside paper.

Having now indicated in a general way the nature and purpose of this invention, there follows a more detailed description of preferred embodiments thereof with reference to the accompanying drawing in which:

Figure 1 represents a cushioning sheath, with parts in cross section, prepared by forming a homogeneous material into tubular form. Figure 2 is an end view of Figure 1. Figure 3 represents a cushioning sheath, with parts in cross section, prepared from a granular material. Figure 4 is a view along line AA of Figure 3.. Figure 5 represents a cushioning sheath with parts in cross section prepared in corrugated form. Figure 6 is an end view of Figure 5.

The above listed figures will be described, together with like numbers representing like parts. The assembled article of this invention comprises a blasting cartridge I, surrounded by a cushioning sheath 2, comprised of a packed homogeneous material 3, a granular material 4, or a corrugated material 5. The cushioning materials 3, 4, and 5 may be retained in position by a surrounding tube 6, which may also, in some cases, be closed at either or both ends, as shown in Figure 3, with caps I. These closures laid in maintaining the cushioning material, especially that of the granular type 4, in position. The cushioning materials 3, 4, and 5 may be composed of the various materials described hereinbefore and may be preformed into various forms, such as for example, the firmly packed condition shown in Figure 1, the loose granular condition shown in Figure 3, or the corrugated condition shown in Figure 5.

It will be understood that my invention is not limited to the specific forms shown in the drawing, but that alternative embodiments, such as combining the granular or homogeneous material with the corrugated sheath or adding granular material to the homogeneous material is contemplated.

The thickness of the cushioning sheath may be varied to provide varied amounts or cushion-' ing effect. A thickness of about M; inch to about inch is desirable for most purposes. Thus, a sheath to fit around a 1 x 8" dynamite cartridge will be about 1%; inches inside diameter and about 1 inches to about 1 inches outside diameter. The sheath may be of about the same length as the cartridge and may be open at both ends to provide propagation of the explosion to another cartridge. The ends of the cartridge may, however, be closed with plugs or discs of the sheathing composition. With the latter arrangement propagation of the explosion to another cartridge is greatly reduced. This arrangement is preferable where only one cartridge is used in a bore-hole.

The compressible cushioning material and the flame quenching or cooling salt may be fabricated into the sheath by moistening the dry composition, then molding and drying the sheath. A binding agent may be incorporated to bind the ingredients together. The binding agent may also be a cooling salt, such as plaster of Paris. Other binding agents, such as, for example, sodium silicate, clay, etc., may be used.

In the cushioning sheath it will be desirable to include about 10% to about 30% of compressible material and about 40% to about 90% of flame quenching salt.

To illustrate the sheathing of an explosive cartridge to provide the cushioning and flame quenching or cooling effects described, the following examples are cited:

Example I A mixture consisting of 65% by weight of sodium bicarbonate, 10% by weight of diatomaceous earth, 10% by weight of balsa pulp and by weight of clay was moistened with an equal weight of a 10% by weight aqueous solution of sodium bicarbonate. This composition was molded into semi-circular half-sheaths about 8 inches in length and of such size that two of the half-sheaths join to give a sheath of about 1% inches inside diameter and about 1% inches outside diameter. The mold was lined with paper. About. 95 grams of wet composition were required for a half-sheath. The molded halfsheaths were dried for about hours on dowels at a temperature of about 130 F. The dowels and inner paper were then removed from the half-sheaths and the latter dried further in air.

Two of the half-sheaths prepared as described above were then sealed around a 1%" x 8" dynamite cartridge with the aid of mucilage. Strips of gum kraft paper were sealed over each end of the sheathed dynamite cartridge. The latter was then dipped in parafiin.

Example II A mixture consisting of 60 per cent by weight of sodium bicarbonate, 20 per cent by weight of expanded mica pellets and 20 per cent by weight of clay was moistened with an equal weight of water. The wet composition was then extruded through a nozzle inside a prefabricated paper shell having a dowel inside to provide an annular space of inch thickness. The extruded tube had a length of about 8 inches. It was dried in an oven at a temperature of about 150 C. for about 20 hours with the dowel inside. The

dowel was then removed. The extruded tube contained about grams of dry composition.

A 1%" x 8" dynamite cartridge was inserted in the extruded tube, the ends sealed with gum kraft paper and the sheathedvcartridge dipped in paraflin.

Example III A mixture consisting of 20 per cent by weight of bagasse and 80 per cent by weight of plaster of Paris was pelleted by moistening the dry composition and agitating the mixture while it was setting. After drying for about 5 hours at a temperature of about F. the dry pelleted material was poured into the annular space between a 1%" x 8" dynamite cartridge and an outer paper shell 1% inches in diameter. The paper on the ends was folded over and the sheathed cartridge dipped in parafiln.

In the above examples, each end of the sheathed cartridge may be fitted with a plug or disc of the cushioning composition used. The plug or disc may have a thickness equal to the thickness of the cushioning sheath, for example, about ,4; inch to another 54 inch. It may have a diameter equal to that of the dynamite cartridge itself, in which case it may fit into the end of the sheath. It may, if desirable, have a diameter equal to the outside diameter of the cushioning sheath, in which case it will fit over the end of the sheath. The plug or disc may be secured at each end by any convenient means such as, for example, by sealing with gum kraft paper.

When used in coal mining the sheathed, cushioned cartridge produced as described in the above examples will provide an improved quality and quantity of lump coal over that obtained with an unsheathed and uncushioned cartridge.

It will be appreciated that the above details and examples are given merely for the purposes of illustrating my invention and are not intended to limit the invention. Moreover, many variations in the compositions and procedures employed may be made without departing from the scope of the invention.

What I claim and desire to protect by Letters Patent is:

1. An improved blasting assembly including an explosive cartridge surrounded by a preformed, annular, tubular sheath comprising an admixture of expanded mica pellets and a flame quenching salt, said sheath characterized by a semirigid, cellular, favose structure which is adapted to provide a cushioning action for the initial explosive shock.

2. An improved blasting assembly including an explosive cartridge surrounded by a preformed, annular, tubular sheath having end closures inserted therein, said sheath and end closures comprising an admixture of expanded mica pellets and a flame quenching salt, said sheath characterized by a semi-rigid, cellular, iavose structure which is adapted to provide a cushioning action for the explosive shock.

3. An improved blasting assembly including an explosive cartridge surrounded by a preformed, annular tubular sheath comprising an admixture of expanded mica pellets, a flame-quenching salt and a binder, said sheath characterized by a semi-rigid, cellular, favose structure which is adapted to provide a cushioning action for the initial explosive shock.

4. An improved blasting assembly including an explosive cartridge surrounded by a preformed,

annular tubular sheath comprising an admixture of expanded mica pellets, and sodium bicarbonate, said sheath characterized by a semirigid, cellular, favose structure which is adapted to provide a cushioning action for the initial explosive shock.

5. An improved blasting assembly including an explosive cartridge surrounded by a preformed, annular tubular sheath comprising an admixture of expanded mica pellets, sodium bicarbonate and a binder, said sheath characterized by a semirigid, cellular, favose structure which is adapted 10 plosive shock.

to provide a cushioning action for the initial explosive shock.

6. An improved blasting assembly including an explosive cartridge surrounded by a preformed, annular tubular sheath comprising an admixture of expanded mica pellets, sodium bicarbonate and clay, said sheath characterized by a semirigid, cellular, favose structure which is adapted to provide a cushioning action for the initial ex- JACOB BARAB. 

